Display screen with a transitional graphical user interface



FIG. 1 is a front view of a display screen with a transitional graphical user interface showing the new design in a first state; and,

FIG. 2 is a front view thereof showing the new design in a second state.

The appearance of the image transitions sequentially between the images shown in FIGS. 1-2. The process or period in which an image transitions to another forms no part of the claimed design.

The broken line showing of the display screen and the element within the display screen forms no part of the claimed design. 

The ornamental design for a display screen with a transitional graphical user interface, as shown and described. 